PROBLEM TO BE SOLVED: To reduce the both pressure fluctuations of a tunnel retreating wave and a tunnel microbarometric wave by specifying the shape of an opening 6 part of tunnel buffer works 5.
SOLUTION: In the tunnel buffer works 5 comprising a tunnel-shaped lining body 2 and the rectangular opening 6 provided in the lining body 2, one side of the opening 6 is faced to the opening side end face 5a of the buffer works 5. This constitution eliminates the vertical one side of the opening part 6 so as to eliminate the generation of the pressure fluctuation. Though one vertical side of the opening 6 remains in the other side, the frequency of the pressure fluctuation can be reduced. This reduction of the pressure fluctuation can reduce the frequencies of oscillating the fittings of adjacent houses, reduce the vibration amplitude of the fittings, and mitigate the rattling of the fittings. The rectangular opening can also reduce the tunnel microbarometric wave.